diff --git a/Text/XML/XSD/DateTime.hs b/Text/XML/XSD/DateTime.hs
--- a/Text/XML/XSD/DateTime.hs
+++ b/Text/XML/XSD/DateTime.hs
@@ -113,10 +113,10 @@
 seconds (Just d) = '.' : d
 seconds Nothing = []
 
-showi :: (Num a, Ord a) => a -> String
+showi :: (Show a, Num a, Ord a) => a -> String
 showi n = (if n < 10 then ('0':) else id) (show n)
 
-showy :: (Num a, Ord a) => a -> String
+showy :: (Show a, Num a, Ord a) => a -> String
 showy n = let k t = if n < t then ('0':) else id
           in k 1000 (k 100 (k 10 (show n)))
 
diff --git a/xsd.cabal b/xsd.cabal
--- a/xsd.cabal
+++ b/xsd.cabal
@@ -1,5 +1,5 @@
 Name:                xsd
-Version:             0.3.5
+Version:             0.3.6
 License:             BSD3
 License-File:        LICENSE
 Synopsis:            XML Schema data structures